Add option to define maximum memory

[inkeliz]

Currently, seems that any code can increase the memory without any soft-limit. That means that one WASM with for { r = append(r, make([]byte, 10_000)...) } will run and will take, eventually, all the memory available.

I would like to limit each runtime/wasm to have ~10MB, for example. Then the wasm must panic/crash due to "Out-Of-Memory" and the grow call must fail.

Also, would be interesting to limit the CPU usage, but I think it's hard to track the CPU usage, that could be more useful when WASM supports thread directly.

[codefromthecrypt]

I suspect that growing to memory.max (pages aka 64KB/page) is enforced per module. So, I suppose what you mean is to have a runtime config for a max for any instantiated module. Since memory so often leaves max undefined[1], it may be the case that this has to fail at runtime instead of instantiation time. Do I understand correctly?

[1] https://www.w3.org/TR/wasm-core-1/#memory-types%E2%91%A0

[codefromthecrypt]

Another way, if you aren't using multiple modules per runtime, is to allow a configuration of memory.max when it wasn't set by the source wasm. This would be simpler and have the same effect.

[codefromthecrypt]

ex.

m, err := r.CompileModule(source)
m.WithMemoryMax(5) // 5*64KiB max unless the existing max was less.

[inkeliz]

I suspect that growing to memory.max (pages aka 64KB/page) is enforced per module. So, I suppose what you mean is to have a runtime config for a max for any instantiated module. Since memory so often leaves max undefined[1], it may be the case that this has to fail at runtime instead of instantiation time. Do I understand correctly?

[1] https://www.w3.org/TR/wasm-core-1/#memory-types%E2%91%A0

I think you get the idea. I would like to enforce that any code can only take ~10MB, for example. It either crashes on initialization (when the minimum memory is larger than the maximum) or during runtime (when calling grow).

---

I did one test modifying the internal/wasm/memory:

wazero/internal/wasm/memory.go

Line 15 in 40c09b8

MemoryMaxPages = MemoryPageSize

Modifying to MemoryMaxPages = uint32(192) seems to force my wasm to crash when using ~8MB, which is expected. So, it seems to work. However, that package is internal/private.

[codefromthecrypt]

So, the limit is applied per-memory and since there can only be one memory per module, the simplest and cheapest way is to limit this per module. I'll raise a configuration to backfill memory.max via runtimeconfig with notes on this later today. thanks for the elaboration!

[codefromthecrypt]

#419